Garmin 396 Reception Problems - Again

[Mike Spera]

Its bbbbaaaaaaacccccckkkkkkk.

I thought we had the 396 reception problems solved with the unit swap
and upgraded firmware. On climb out the thing lost its lock again and
continued to do so until I changed course. That ain't gonna be an option
on a plan in IMC (uh, center, I need to change heading 30 degrees or so
to get my VFR GPS back on line...).

I tried switching freqs. on the nav and com radios to avoid harmonic
interference. No difference. I wonder why this cropped up after 3+
months of problem free reception??? Last time this was happening, I
tried running the unit on batteries, switching the GPS antenna around,
and a host of other things. Nothing helped until I upgraded the firmware
on a new unit. It has been solid since then with 6+ sats near the top.

Now, garbage again.

Anyone else see this problem on theirs?

Thanks,
Mike

[Dan Luke]

"Mike Spera" wrote:

> Now, garbage again.
>
> Anyone else see this problem on theirs?
>

Never on my 396, but yes on my 496. It was the antenna.

What model of antenna are you using?

[Dan[_1_]]

Had the same issue.

Traced it to a bad antenna. Garmin FedEx'ed me a new one. The problem
is demonstrated when in line of sight to cell phone towers on certain
frequencies. Test it out around town, and you'll see what I mean.

--Dan

Mike Spera wrote:
> Its bbbbaaaaaaacccccckkkkkkk.
>
> I thought we had the 396 reception problems solved with the unit swap
> and upgraded firmware. On climb out the thing lost its lock again and
> continued to do so until I changed course. That ain't gonna be an option
> on a plan in IMC (uh, center, I need to change heading 30 degrees or so
> to get my VFR GPS back on line...).
>
> I tried switching freqs. on the nav and com radios to avoid harmonic
> interference. No difference. I wonder why this cropped up after 3+
> months of problem free reception??? Last time this was happening, I
> tried running the unit on batteries, switching the GPS antenna around,
> and a host of other things. Nothing helped until I upgraded the firmware
> on a new unit. It has been solid since then with 6+ sats near the top.
>
> Now, garbage again.
>
> Anyone else see this problem on theirs?
>
> Thanks,
> Mike

[Doug Vetter]

Mike Spera wrote:
> Its bbbbaaaaaaacccccckkkkkkk.
>
> I thought we had the 396 reception problems solved with the unit swap
> and upgraded firmware. On climb out the thing lost its lock again and
> continued to do so until I changed course. That ain't gonna be an option
> on a plan in IMC (uh, center, I need to change heading 30 degrees or so
> to get my VFR GPS back on line...).
>
> I tried switching freqs. on the nav and com radios to avoid harmonic
> interference. No difference. I wonder why this cropped up after 3+
> months of problem free reception??? Last time this was happening, I
> tried running the unit on batteries, switching the GPS antenna around,
> and a host of other things. Nothing helped until I upgraded the firmware
> on a new unit. It has been solid since then with 6+ sats near the top.
>
> Now, garbage again.
>
> Anyone else see this problem on theirs?
>
> Thanks,
> Mike

Hmmmm. Interesting. I was just about to send my unit in. Now I wonder
if I should.

I did pretty much every troubleshooting procedure I could think of,
including Garmin's own "hard reset" procedure, running with the master
switch off in flight for about 5 minutes to positively eliminate
aircraft radios as a problem, running on battery, swapping antennas,
power cycling it, leaving it off for 5-10 minutes, etc. etc. etc. All
to no avail.

Incidentally, I have a GNS430 in the panel and compared satellite
reception when the 396 went deaf. The 430 had 12 sats with the signal
bars maxed on 9 of them. This is not the result of localized GPS
jamming tests. It may, however, be the result of terrestrial
transmissions combined with poor shielding of the 396's receiver. It's
happened several times in my local flying area (New Jersey) but it's
also happened over the Carolinas and Virginia.

Garmin has told me I'm running the latest powered antenna (it's a 2x3"
rectangular unit...I forget the model number). The earlier square units
apparently had problems.

I'm running firmware version 3.6 and have seen this problem since
version 3.0, which was (interestingly enough) installed when it was
about 3 months old.

I have a copy of the 2.4, 2.6, and 2.8 firmware -- all of which were
trouble-free -- and as a last ditch effort I'm planning to downgrade to
one of those (likely 2.8). Garmin has said that should work. If it
doesn't it won't have far to fall into the shipping box.

Good luck.

-Doug

--------------------
Doug Vetter, ATP/CFI

http://www.dvatp.com
--------------------

[Doug Vetter]

Dan wrote:
> Had the same issue.
>
> Traced it to a bad antenna. Garmin FedEx'ed me a new one. The problem
> is demonstrated when in line of sight to cell phone towers on certain
> frequencies. Test it out around town, and you'll see what I mean.

Dan,

I've noticed that when my unit goes deaf, switching antennas from the
external "hockey puck" unit to the stubby vertical has no effect so we
may be talking about the same symptoms but a different cause.

Just curious -- did they replace your puck antenna with a new model or
just replace the one you had? Also, just so we can nail this down, what
model antenna do you have now?

-Doug

--------------------
Doug Vetter, ATP/CFI

http://www.dvatp.com
--------------------

[B A R R Y[_1_]]

Doug Vetter wrote:
>
> I've noticed that when my unit goes deaf, switching antennas from the
> external "hockey puck" unit to the stubby vertical has no effect so we
> may be talking about the same symptoms but a different cause.

Our 196 has the same problem. Switching antennas has no effect.

[Gene Seibel]

Any tall TV towers in the area? Some high power UHF stations have
harmonics that fall on GPS frequencies.
--
Gene Seibel KB0NNN
http://pad39a.com/gene/broadcast.html
Because I fly, I envy no one.



Mike Spera wrote:
> Its bbbbaaaaaaacccccckkkkkkk.
>
> I thought we had the 396 reception problems solved with the unit swap
> and upgraded firmware. On climb out the thing lost its lock again and
> continued to do so until I changed course. That ain't gonna be an option
> on a plan in IMC (uh, center, I need to change heading 30 degrees or so
> to get my VFR GPS back on line...).
>
> I tried switching freqs. on the nav and com radios to avoid harmonic
> interference. No difference. I wonder why this cropped up after 3+
> months of problem free reception??? Last time this was happening, I
> tried running the unit on batteries, switching the GPS antenna around,
> and a host of other things. Nothing helped until I upgraded the firmware
> on a new unit. It has been solid since then with 6+ sats near the top.
>
> Now, garbage again.
>
> Anyone else see this problem on theirs?
>
> Thanks,
> Mike

[Mike Spera]

>
> I've noticed that when my unit goes deaf, switching antennas from the
> external "hockey puck" unit to the stubby vertical has no effect so we
> may be talking about the same symptoms but a different cause.
>



I tried the stubby when the thing used to crap out and it did exactly
the same thing.

Mike